Corrosion inhibitor in dry cell battery



United States Patent Ofiice 3,291,645 Patented Dec. 13, 1966 3,291,645CORROSION INHIBITOR IN DRY CELL BATTERY Lawrence P. Gould, Syracuse,N.Y., assignor to Allied Chemical Corporation, New York, N.Y., acorporation of New York No Drawing. Filed Sept. 10, 1964, Ser. No.395,551

5 Claims. (Cl. 136-107) This invention relates to dry cell batteries andmore particularly refers to a new and improved dry cell battery andmethod for reducing corrosion in batteries.

Ammonium chloride is an essential ingredient in common dry cells such asflashlight batteries. The ammonium chloride in solution form and incrystal form with other ingredients is sealed in a zinc can having therequired dimensions of the battery.

When the battery is made an undesirable chemical reaction occurs whichtends to corrode the zinc can. This wasteful corrosion of zincdiminishes the shelf life of the battery and decreases the servicecapacity of the battery. The problems and difficulties involved incorrosion of zinc in dry cell batteries has engaged the attention ofresearchers for many years as exemplified by the article entitled Effectof Inhibitors on the Corrosion of Zinc in Dry-Cell Electrolytes, U.S.Department of Commerce National Bureau of Standards, Research PaperRP1863, vol. 40, February 1948; the article in the Journal of theElectrochemical Society, vol. 99, No. 8, August 1952, pages 179C to187C, wherein the authors state, It is the wasteful corrosion of zinc,rather than its anodic behavior in the operating cell, that has demandedthe attention of the battery technologist, and Even today, the wastefulcorrosion of zinc in cells on long time intermittent service may be asmuch as 50 percent as great as the weight of metal utilized ingenerating current, and The problem of finding corrosion inhibitors,other than mercury, effective under the variable conditions of celldischarge and compatible with the standard dry battery ingredients, hasnot proved a simple task; and the more recent article in the Journal ofApplied Chemistry, 10, April 1960, entitled Corrosion of Zinc, I,Corrosion in Impure Ammonium chloride Solution by F. G. Stickland, pages15517l.

An object of the present invention is to provide an additive which willreduce the corrosion of zinc by ammonium chloride in a dry cell battery.Other objects and advantages of the present invention will be apparentfrom the following description.

In accordance with the present invention corrosion of zinc by ammoniumchloride in a dry cell battery is materially reduced by theincorporation of an additive having the formula RSO NHCH COOM wherein Ris an ali phatic hydrocarbon radical containing 8-20 carbon atomsinclusive, preferably 12-14 carbon atoms inclusive and M is an alkalimetal preferably sodium. The preferred additive is one wherein R islauryl and M is sodium.

The additives of the present invention are highly effec' tive and onlyvery minute quantities of the order of 50 parts per million or lessbased on the amount of ammonium chloride are needed to materially reducecorrosion. Larger amounts may be employed and up to about 2000 ppm.effect further reduction in corrosion. Quantities above 2000 ppm. may beemployed but do not give much additional benefit.

The additives may be incorporated in the battery in any convenient way.A preferred method is to uniformly distribute the additive throughoutthe ammonium chloride prior to its incorporation in the battery. Thismay be accomplished by dissolving the additive in a volatile solvent andthe solution 'added'to hot dry crystals of ammonium chloride in a mixingconveyor. By this method a solvent is distributed over the crystals andevaporated by the sensible heat of the crystals leaving the additive inthe form of thin film over the crystal surface. In another method theadditive may be dissolved or suspended in a clear, hot, agitated liquorin the ammonium chloride process prior to crystal formation. By thismethod, the additive is distributed uniformly over the crystals so thatas the crystals are subsequently filtered, dried and screened, theadditive is thoroughly mixed with the crystals.

The following example illustrates the present invention.

The test procedure was that published by the British StandardsInstitution No. 3448 in 1961 with the modification of 50 C. for 24 hoursinstead of the lower temperature for a longer time. In this testprocedure the hydrogen evolved is measured by weighing the electrolytedisplaced to the nearest 0.1 gram. The lower this figure the less thecorrosion. In Table I below are given the experimental results of theeffect of the additive on corrosiveness toward zinc in comparison with atest without an additive.

Although certain preferred embodiments of the invention have beendisclosed for purposes of illustration, it will be evident that variouschanges and modifications may be made therein without departing from thescope and spirit of the invention.

I claim:

1. A method of reducing corrosion of zinc in an ammonium chloride drycell battery electrolyte which comprises incorporating in saidelectrolyte an additive having the formula RSO NHCH COOM wherein 'R isan aliphatic hydrocarbon radical containing 8-20 carbon atoms inclusiveand M is an alkali metal.

2. A method as claimed in claim 1 wherein the additive is in an amountof about 50 parts per million to about 2000 parts per million based onthe amount of ammonium chloride.

3. A method as claimed in claim 1 wherein R is an aliphatic hydrocarbonradical containing 12-14 carbon atoms inclusive and M is sodium.

4. A method as claimed in claim -1 wherein in the formula R is lauryland M is Na.

5. A dry cell battery comprising a zinc electrode in contact with anammonium chloride electrolyte, said electrolyte having an additiveincorporated therein having the formula RSO NHCH COOM wherein R is analiphatic hydrocarbon radical containing 8-20 carbon atoms inelusive andM is an alkali metal to reduce corrosion of zinc by ammonium chloride inthe dry cell battery.

References Cited by the Examiner UNITED STATES PATENTS Michel et a1.252391 X Klopp 136107 Zimmerman et a1. 136-161 Spivack et a1 252-391 X 4OTHER REFERENCES WINSTON A. DOUGLAS, Primary Examiner.

D. L. WALTON, Assistant Examiner.

1. A METHOD OF REDUCING CORROSION OF ZINC IN AN AMMONIUM CHLORIDE DRYCELL BATTERY ELEECTROLYTE WHICH COMPRISES INCORPORATIONG IN SAIDELECTROLYTE AN ADDITIVE HAVING THE FORMULA RSO2NHCH2COOM WHEREIN R IS ANALIPHATIC HYDROCARBON RADICAL CONTANING 8-20 CARBON ATOMS INCLUSIVE ANDM IS AN ALKALI METAL.